Quick recap
Hastings returns from Argentina to find Poirot about to leave for Rio de Janeiro. The trip is called off when a man bursts into the flat, scrawls the number 4 over and over, and dies. So begins the hunt for the Big Four, a gang bent on ruling the world: a Chinese mastermind, an American millionaire, a French scientist and Number Four, a killer and master of disguise. The cases jump around England and Europe. Poirot even fakes his own death and invents a twin brother, Achille. In the end he storms the gang's hideout in the Italian mountains, rescues Hastings's kidnapped wife and brings the organization down.
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